In a sealing apparatus for sealing foil material, two or more foils are fed to a sealing means and are there sealed together with the aid of a sealing head which is lowered onto the joined foils and transmits heat to the foils at the desired places. Insofar as sealing or sealing means is referred in the present text, this includes a hot bonding process in which an adhesive material is applied between the foils to join the foil materials by heat.
Such a sealing process is e.g. used in the production of foil bags, e.g. foil bags for beverages. Two foil materials are laid one upon the other to form the side foils of the foil bag. A bottom foil is possibly interposed in an edge portion. The foils are sealed together at two directly superimposed edges of the side foil material and at the third edge where the bottom foil is optionally positioned. The fourth edge of the respective foil materials is closed by sealing after the foil bag has been filled. An example of such a foil bag is e.g. shown in FIG. 3 where the weld seams 33 are formed in the first-described process and the weld seam 34 is formed after the foil bag has been filled.
In an automated production plant, foil webs are supplied for sealing purposes, with the webs being cut after the sealing process so as to form individual units. The foil webs are placed one upon the other and guided below the sealing head. The head is lowered. In doing so, it must cover a lowering distance of a few centimeters. After having been pressed onto the foil materials, the sealing head is again lifted and the foil webs are further transported by a distance corresponding to one foil bag before the sealing head is again lowered onto the foil material that has been transported further away. To achieve a high throughput, the sealing head is kept at a constantly high temperature to make time-consuming heating and cooling processes superfluous. Therefore, it is necessary that in the operative states in which no sealing operation takes place the sealing head should be so remote from the foil material that the foil material is not overheated or scorched. Such a distance is e.g. required in cases where the entire sealing apparatus has been stopped to eliminate a malfunction.
However, in an automated manufacturing plant, the lifting and lowering movement of the sealing head, which amounts to a few centimeters, takes an undesired long period of time at the throughput rates which are nowadays possible.